After so many close shaves, this was a night when everything came together for Millwall on the road in a match that will live long in the memory of the 377 visiting supporters – and many more watching at home – that made the long trek up to DE24 on a chilly midweek evening.

In truth, the Lions have threatened to produce this kind of result over the course of the season, but certain aspects have prevented their game plan from being executed to perfection.

Well, not this time.

And suddenly, Millwall fans can look at the Championship table without hiding behind their sofas as they moved five points clear of that dreaded dotted-line, having played a game fewer than the majority of the sides around them.

So, where does this result rank? A close second to the 4-3 victory at Leeds United in January seems appropriate in terms of their best on the road since the Lions were promoted back to the second tier just under two years ago.

Neil Harris echoed those thoughts. “We didn’t create a lot ourselves, but sometimes when you’re the away side you only need one,” he said. “We are really pleased. It is certainly one of the best away performances from my time in charge.”

After the highs of reaching the FA Cup quarter-finals at AFC Wimbledon last Saturday, combined with an enticing draw against Premier League side Brighton & Hove Albion in the last eight, questions were raised as to whether Millwall would be up for the nitty-gritty challenge of a relegation battle and be able to shift their attention away from the excitement of a potential semi-final at Wembley at the beginning of April.

Too right they were. They did everything required, and more. The fact that goalkeeper Jordan Archer wasn’t called into action until added-time told its own story.

Millwall did a job on Frank Lampard’s depleted Derby, who missed the opportunity to climb back into the top-six. They have clinched a league double over the Rams.

Despite enjoying almost 66 per cent of the ball and making more than double the number of successful passes compared to the South Londoners, Derby were unable to break down a determined and well-drilled Lions back four.

They didn’t even get close. When they did threaten, either Jake Cooper or Shaun Hutchinson were on hand to mop up and snuff out any potential danger. The hosts were limited to long-range shots, the majority of which sailed into the stands.

In terms of chances, well, there weren’t many. Tom Huddlestone drilled over from 25-yards in the opening period, which was the only meaningful attempt in a relatively drab first 45 minutes.

Another sign of how comfortable Millwall were was the fact that the hosts were booed off at the break. Jack Marriott should have turned those jeers into cheers moments after the restart, but the former Peterborough United forward scuffed his shot after producing a wonderful touch to beat Cooper initially, before the Lions defender recovered to clear the danger.

Jed Wallace skimmed the top of the Rams crossbar from a cross just before the hour mark, but just 16 minutes later Millwall’s number seven would go one better and bag his fifth Championship goal of the campaign. Four of those have come against teams that sit in the top seven.

Ironically, it came from a Derby free-kick. Lee Gregory pounced on an uncharacteristic mistake from the impressive Ashley Cole before skipping two challenges. He was fouled but managed to find Shane Ferguson, who set Wallace away with an exquisite first-time pass.

Cole managed to recover from his error, but was unable to get close enough to Wallace, allowing him to shift onto his weaker foot and lash past Kelle Roos.

The ex-Dons loanee keeper could possibly have dealt better with the shot.

Wallace had missed chances late in the games at Middlesbrough and AFC Wimbledon on Saturday, but not this time.

Pride Park had been silenced, although it was hardly ear-splitting prior to that. All you could hear was a small pocket of visiting fans in the far corner going absolutely bonkers at the thought of just their second away league victory in nine months.

Apart from a stoppage-time header from Fikayo Tomori, that Archer comfortably palmed away, Millwall navigated through the latter stages with an element of ease, as if they’d been doing this kind of thing all season. It was their first Championship three points since New Year’s Day and earned them their first league double over Derby for almost 50-years.

There would be no celebratory Domino’s this time, but Millwall travelled back down the M1 knowing they are one step closer to ensuring a third consecutive season at Championship level.